In the function ConvertToPostgresFormat in pkg/postgres/time/time.go, which seems to be used specifically for recovery_target_time, the conversion of an RFC3339 or RFC3339Micro input string results in a trailing Z for UTC times.

This is producing an error in recovery clusters. You can see the discussion in cloudnative-pg/cloudnative-pg#8937
and some experiments in cloudnative-pg/cloudnative-pg#8981

Specifically, given an input time in RFC3339 format, in UTC time zone, we get the following:

"msg":"waiting for server to start....2025-10-28 16:40:20.324 UTC [38] 
  LOG:  invalid value for parameter \"recovery_target_time\": \"2025-10-28 16:34:15.000000Z\"",

According to the Postgres documentation on recovery_target_time, the same format used for timestamps is valid, EXCEPT that timezone abbreviations are not allowed, and numeric offsets from UTC are recommended.

The value of this parameter is a time stamp in the same format accepted by the timestamp with time zone data type, except that you cannot use a time zone abbreviation (unless the timezone_abbreviations variable has been set earlier in the configuration file). Preferred style is to use a numeric offset from UTC, or you can write a full time zone name, e.g., Europe/Helsinki not EEST.

https://www.postgresql.org/docs/current/runtime-config-wal.html

If ConvertToPostgresFormat substitutes +00 for Z when formatting UTC times, the recovery time will work fine.

Again, see cloudnative-pg/cloudnative-pg#8981 for the green runs.

In addition, we don't currently have an E2E test that properly exercises the ConvertToPostgresFormat function, as the present implementation uses a Postgres timestamp in the cluster spec, which passes through the Convert function. The E2E will be fixed to use a recovery target timestamp in RFC3339.